Macular degeneration is a clinical term that is used to describe a family of diseases that are all characterized by a progressive loss of central vision associated with abnormalities of Bruch's membrane, the choroid, the neural retina and/or the retinal pigment epithelium. These disorders include very common conditions that affect older subjects (age-related macular degeneration or AMD) as well as rarer, earlier-onset dystrophies that in some cases can be detected in the first decade of life. Other maculopathies include North Carolina macular dystrophy, Sorsby's fundus dystrophy, Stargardt's disease, pattern dystrophy, Best disease, and Malattia Leventinese.
Age-related macular degeneration (AMD), the most prevalent macular degeneration, is associated with progressive diminution of visual acuity in the central portion of the visual field, changes in color vision, and abnormal dark adaptation and sensitivity. Two principal clinical manifestations of AMD have been described as the dry, or atrophic, form, and the wet, or exudative, form. The most significant risk factor for the development of both forms are age and the deposition of drusen, abnormal extracellular deposits, behind the retinal pigment epithelium (RPE). Drusen causes a lateral stretching of the RPE monolayer and physical displacement of the RPE from its immediate vascular supply, the choriocapillaris. This displacement creates a physical barrier that may impede normal metabolite and waste diffusion between the choriocapillaris and the retina.
Malattia Leventinese (ML), also termed Doyne's honeycomb choroiditis or dominant drusen, is a genetic, early onset form of macular degeneration characterized by numerous, often confluent drusen that may radiate peripherally from the macula. This disease is phenotypically similar to age-related macular degeneration (AMD). The occurrence of sub-RPE deposits in ML make it a valuable model for understanding pathways that participate in age-related macular degeneration (AMD).